Bone intramedullary fixation scaffold

ABSTRACT

A new shape changing bone implant and instrument for the fixation of structures to include bone tissue. This new implant stores elastic mechanical energy to exert force on fixated structures to enhance their security and in bone affect its healing response. This unique implant locks into bone and then simultaneously expands and shortens to lock into bone and then pull the bone segments together. This implant once placed changes shape in response to geometric changes in the implant&#39;s and bone&#39;s materials structure. The implant may be fabricated from any biocompatible material that acts elastically when deformed including but not limited to nitinol, stainless steel, titanium, and their alloys as well as polymers such as polyetheretherketone, silicone elastomer and polyethylene. The implant is advanced over prior devices due to its: (1) method of operation, (2) high strength, (3) method of insertion, (4) compressive force temperature independence, (5) energy storing implant retention and delivery system, (6) compatibility with reusable or single use product configuration, (7) ability to act as a scaffold to conduct healing bone through the implant, (8) efficient and cost effective manufacturing methods, and (9) reduction in the steps required to place the device.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This application claims priority to U.S. Patent Appl. Ser. No.62/155,032, filed Apr. 30, 2015, entitled “Bone Intramedullary FixationScaffold,” which is hereby incorporated herein by reference in itsentirety for all purposes.

TECHNICAL FIELD

This application relates to implants used for fixation of bone of themusculoskeletal system and the methods for their use and morespecifically to implants that reside within bone and that are caused tochange shape through their metallurgic properties and their interactionwith mechanical instruments to pull together and compress bone.

BACKGROUND

Bone screws and wires have been in clinical use for decades for bonefixation. These important bone fixation devices have evolved from rigidstainless steel or titanium wires and screws to shape changing nitinolimplants that through their expansion are fixated in bone. Theseimplants are commonly placed along the centerline of bone and thusreside within the bone's intra-medullary canal.

The early rigid bone fixation devices were commonly threaded or drilledinto bone where the more modern devices are implanted in drilled holesand expand through mechanical means to lock into bone but none, otherthan the invention described herein, lock into bone and then shorten topull together and compress the bony segments. Intra-medullary bonefixation technology includes: (1) wires, (2) screws, (3) multi-componentscrews, (4) heat sensitive shape memory alloy implants cut from plates,and (5) polymer pins intended to degrade over time.

The implant embodiments of the present invention have advantages overthe prior art because they store mechanical energy and impart thatenergy to bone through shape change and predictable bone-to-bonecompression. The implant embodiments of the present invention pulltogether and compress bone to promote healing. The implant embodimentsof the present invention are hollow, which allow bone to grow within theimplants so as to further lock the implant into bone and conduct newbone through the implants' lumen to bridge bones intended to healtogether.

Some prior art implants may change shape or be caused to change shapebut do not lock into the separate bone segments and then act to pulltogether and compress bone.

Instruments, to place the implants into bone, complements the implants'method of action by holding the implants extended and at their minimumdiameter, allowing the implants to be manipulated in bone, releasing theimplants when fully inserted, and protecting the implants duringhandling and shipment.

As will be clear in the following detailed description of the prior art,the embodiments disclosed and taught in the present Application overcomethe prior art deficiencies in ease of use, manufacturing, mode ofoperation, strength, cost and allows hospital procedures that limitdisease transmission.

Expanding and Bone Locking Implants

The embodiments of the present invention overcome the deficiencies ofother within bone fixation implants such as (1) requiring heating orcooling, (2) having a temperature dependent fixation force, (3)requiring ancillary equipment to manipulate the implant, (4) beingimplanted in the soft martensitic phase of nitinol, (5) requiring anexpensive multiple step manufacturing process to set both the stapleshape and transition temperatures, and (6) others that become more clearin the review of the embodiments of the present invention.

The embodiments of the present invention overcome the deficiencies ofthe prior elastic staples and intramedullary bone shape changing bonefixation devices such as (1) providing the surgeon limited time to placeit in bone, (2) designs that cannot contract their length, (3) requiringexpensive ancillary equipment to manipulate the implant, (4) cooling ofthe implant prior to opening for placement, (5) designs that can notsimultaneously expand to lock into bone and contract to pull togetherand compress bone, and (6) others deficiencies that will become moreclear in the review of the embodiments of the present invention.

Instrument and Implant Devices And Methods

The foregoing discussion illustrates the deficiencies of the prior artand the lack of a simple shape changing bone fixation implant,instrument for its implantation and method of use consistent with thedemands of surgery. Product packaging may be in reusable hospitalsterilization tray and a manufactured sterile kit containing the implantand instruments required for surgery. In the discussion of theembodiments of the subject invention its benefits will be realized as asimple, reliable, low cost solution to present an elastic energy storingshape changing staple to bone and releasing the staple so that it canpull together and compress bone even in the presence of gaps that canform during bone healing.

SUMMARY OF THE INVENTION

The embodiments of the subject invention describe an improved withinbone fixation implant that stores recoverable mechanical energy in itsstructure and changes shape to pull together and compress the bonefixation interface. Any biocompatible that has structural properties andbehaves elastically when deformed such as but not limited to nitinol,titanium, and stainless steel, as well as a number of polymerspolyetheretherketone, silicone elastomers and polyethylene. Thisimplant, instrument, and method have multiple advantages over priorimplants: (1) shape change and compression forces are temperatureindependent, (2) the implant does not require heat or cooling toactivate it, (3) the implant does not need to be stretched ormechanically manipulated by the surgeon to facilitate implantation, (4)the surgeon's sole required effort, pushing the implant into bone andreleasing it while the implant automatically controls the implantmechanism of shape change and compression, (5) the implant load transferto bone can be controlled by the surgeon with its instrument to minimizethe chance of implant induced fracture and (6) the implant's bonefixation load is at a maximum and constant during the operativeprocedure.

In certain embodiments, this implant-containing instrument is combinedwith a reusable or disposable extrusion instrument for pushing theimplant through the instrument and into bone. This allows the use ofshape changing implants in reusable and disposable instruments which arepre-sterilized in procedures and under conditions in which the prior artstaples cannot be used.

In general, in one aspect, the invention features a fixation device thatincludes a body that is operable to change shape to expand and shortenthe body. The body includes an elastic material. The body has aplurality of prongs on each of a first end and a second end. The bodyhas a shortening section between the prongs on the first end and thesecond end. The shortening section is operable to shorten the body bymoving from an elongated position to a shortened position.

Implementations of the invention can include one or more of thefollowing features:

The body can be a tubular shape.

The shortening section can form an expanded bulge when operated toshorten the body.

The expanded bulge can be oriented with the long axis of the body.

The fixation device can further include an internal mandrel. Theshortening section can be held in the elongated position with theinternal mandrel.

The internal mandrel can include grooves to receive a locking plate.

The internal mandrel can include a cross sectional shape in a firstsection of the internal mandrel. The first cross sectional shape can bedifferent in shape than other sections of the internal mandrel.

The cross sectional shape can be a square shape, a rectangular shape, ahexagonal shape, a triangular shape, or a non-round shape.

The fixation device can further include a lock plate and a lumen. Thelock plate can be integral to the lumen.

The lock plate can be operable to interact with the internal mandrel sothat the lock plate is operable to rotate between a locked position andan unlocked position.

The fixation device can further include an external sleeve. Theshortening section can be held in the elongated position with anexternal sleeve.

The fixation device can further include a plurality of fenestrations anda lumen. The fenestrations can provide openings into the lumen.

The fenestrations and lumen can be positioned to allow bone ingrowthinto the body.

The first end can be slotted and the second end can be slotted so thateach of the first end and the second end is capable of bending toconform to the internal anatomy of bone.

The prongs in the plurality of prongs can extend outward from the body.

The prongs can be twisted in a twist direction.

The twist direction of the prongs can be positioned so that when thebody is turned in a first direction the prongs deflect inward.

The twist direction of the prongs can be positioned so that when thebody is turned in a second direction the prongs deflect outward.

The fixation device can be operable for use in a medical procedure.

The elastic material can include an elastic metal that is nitinol,stainless steel, titanium, or an alloy thereof.

The elastic material can include an elastic polymer that ispolyetheretherketone, silicone elastomer, polyethylene, or a combinationthereof

In general, in another aspect, the invention features a method offixating a first bone and a second bone. The method includes the step ofselecting an implant having a first bone locking feature at a first endand a second bone locking feature at a second end.

The method further includes the step of locking the first bone lockingfeature to the first bone. The method further includes the step oflocking the second bone locking feature to the second bone. The methodfurther includes the step of shortening the implant between the firstbone locking feature and the second bone locking feature.

Implementations of the invention can include one or more of thefollowing features:

The implant can allow bone ingrowth.

The implant can have an expandable surface. The method can furtherinclude expanding the expandable surface to lock into the first bone orthe second bone.

The step of shortening the implant can include expanding a surface ofthe implant to shorten length of the implant.

The step of shortening the implant can include contacting an outersurface of the implant to shorten its length.

The shortening of the implant can impart mechanical energy to provideinterfacial pressure between the first bone and the second bone.

The step of providing interfacial pressure can stimulate healing of thefirst bone and the second bone.

In general, in another aspect, the invention features a method offixating a first bone and a second bone. The method includes the step ofmaking holes in the first bone and the second bone to receive animplant. The method further includes the step of inserting a first endof the implant into the first bone. The method further includes the stepof releasing the implant to change shape of the implant within the firstbone. The method further includes the step of placing the second boneover a second end of the implant. The method further includes the stepof pushing the first bone and the second bone together until the firstbone contacts the second bone.

In general, in another aspect, the invention features a fixation devicethat includes a body that is operable to change shape from a first shapeto a second shape. The first shape has a different length than thesecond shape. The body includes an elastic material. The body has aplurality of prongs on each of a first end and a second end. The bodyhas a length changing section between the prongs on the first end andthe second end. The length changing section is operable to change thelength of the body by moving from a first length position to a secondlength position in which the first length position and the second lengthposition are positions having different lengths.

DESCRIPTION OF DRAWINGS

FIG. 1a depicts an embodiment of the present invention of an implant ofin its constrained configuration.

FIG. 1b depicts the implant of FIG. 1a in its released configuration.

FIG. 2a depicts an embodiment of the present invention of an implantconstrained with in its instrument.

FIG. 2b depicts the implant and instrument of FIG. 2a with the implantreleased within its instrument.

FIG. 3a depicts the implant and instrument of FIG. 2a with the implantadvanced and constrained within its instrument in preparation forimplantation into bone.

FIG. 3b depicts the implant and instrument of FIG. 2a with the implantwithin bone prior to implant release.

FIG. 4a depicts the implant and instrument of FIG. 2a with the implantconstrained within instrument showing instrument unlocking.

FIG. 4b depicts the implant and instrument of FIG. 2a with the implantbeing advanced through the instrument into bone.

FIG. 4c depicts the implant and instrument of FIG. 2a with the implantshowing instrument release.

FIG. 5a depicts an implant of an embodiment of the present invention ina first bone.

FIG. 5b depicts the implant of FIG. 5a with the implant in the firstbone and a second bone with a lock plate.

FIG. 5c depicts the implant of FIG. 5a with the implant in the first andsecond bone.

FIG. 6a depicts an end view of an implant of an embodiment of thepresent invention showing direction of rotation to cause disengagementof the prongs from bone.

FIG. 6b depicts the implant of FIG. 6a with a mandrel and a lock platein its constrained configuration.

FIG. 6c depicts the implant of FIG. 6a with the mandrel and the lockplate in its released configuration.

FIG. 7a depicts an embodiment of an alternate implant holding mechanismwith prongs and mandrel.

FIG. 7b depicts the implant holding mechanism of FIG. 7a with thealternate implant holding mechanism within an unconstrained implantlumen.

FIG. 7c depicts the implant holding mechanism of FIG. 7a with thealternate implant holding mechanism locked into constrained implant.

FIG. 8a depicts an embodiment of an alternate external implant holdingmechanism and mandrel adjacent to unconstrained implant.

FIG. 8b depicts the implant holding mechanism of FIG. 8a with thealternate external implant holding mechanism and mandrel within andoverlapping unconstrained implant.

FIG. 8c depicts the implant holding mechanism of FIG. 8a with thealternate external implant holding mechanism and mandrel locked intoconstrained implant.

FIG. 9 depicts use of a K-wire (360) to create a pilot hole in theproximal bone (200).

FIG. 10 depicts use of a drill (370) and drill stop (380) to drill ahole in the distal bone (210).

FIG. 11 depicts use of a drill (370) to drill a hole in the proximalbone (200).

FIG. 12 depicts implantation of the intramedullary fixation scaffold inthe proximal bone (200).

FIG. 13 depicts removal of a locking pin and ring (410) and rotation ofthe instrument knob (120) to release the intramedullary fixationscaffold in the proximal bone (200).

FIG. 14 depicts insertion of the intramedullary fixation scaffold in thedistal bone drill hole (220).

FIG. 15 depicts reduction of the distal bone on the proximal bone andremoval of the lock plate (90).

FIG. 16 depicts insertion of a k-wire (360) through an adjacent jointand through the intramedullary fixation scaffold.

FIG. 17a depicts a lock plate (440) integral to the intramedullaryfixation scaffold with the intramedullary fixation scaffold contractedin its length.

FIG. 17b depicts a lock plate (440) integral to the intramedullaryfixation scaffold with the intramedullary fixation scaffold extended inits length.

REFERENCE NUMERALS

-   10. tubular section-   20. shape changing section-   30. fixation section-   40. bulge expanded-   45. bulge contracted-   50. prongs-   60. push plate-   70. conformation slots-   80. lumen-   90. lock plate-   95. lock plate mandrel release opening-   100. sleeve-   110. handle-   120. knob-   130. knob unlock direction of movement-   140. knob advancement direction of movement-   150. knob implant release direction of movement-   160. implant removal direction of movement for prong disengagement-   170. prong twist angle-   180. mandrel-   190. mandrel head-   200. proximal bone-   210. distal bone-   220. distal bone hole-   230. proximal bone hole-   300. internal locking prongs-   310. internal prong locking tabs-   320. external locking prongs-   330. external prong locking tabs-   340. mandrel for internal locking prongs-   350. mandrel for external locking prongs-   360. K-wire for alignment, creation of a pilot hole and fixating    adjacent joints.-   370. Drill bit-   380. Drill stop-   390. Drill bit handle-   400. Direction of drill rotation-   410. Removable lock pin and ring-   420. Direction of knob rotation to release mandrel-   430 Direction of advance of K-wire to treat adjacent joints-   440 Lock plate integral to the IFS

DETAILED DESCRIPTION

The embodiments of the subject invention includes a tubular implant witha plurality of locking prongs 50, expanding and implant shortening bonelocking bulges 40, fenestrations in its body, and a lumen 80 for boneingrowth and instrument 110 operation.

The implant can be fabricated of any cross section not limited to round,square, hexagonal or triangular that can be formed with a lumen 80. Thelumen 80 forms a hollow core to allow bone to form through the implantand bridge the bone segments it fixates.

This lumen 80 further receives the instrument mandrel 180 to extend theimplant's length and constrain the implant at its greatest length andminimum bulge 45 diameter. The mandrel has at least one section that issquare, rectangular, hexagonal, triangular or other shape other thanround. The mandrel 180, lock plate 90 and implant push plate 60interlock to hold the implant extended, as illustrated in FIG. 6b . Whenthe mandrel 180 is turned, it aligns with the lock plate slot 95removing the implant's constraint and allowing the implant to shortenand the bulges 40 to be in their extended state. The lock plate (440)can be integral to the body and contained within the lumen (80) in analternate embodiment where the lock plate is not removable.

The prongs 50 and bulge 40 lock into bone to resist implant rotation andpull out and pull the bones together to create compression. If implantloosening occurs the bulges 40 will continue to expand furthershortening the implant and causing it to keep pulling the bonestogether.

The constrained implant state of FIG. 1a and the unconstrained state ofFIG. 1b illustrate the shape change that occurs to the implant whenrelease with the instrument. In use, the implant is held within aninstrument 110 with an advance and release knob 120 as shown in FIG. 2a. The instrument has a sleeve 100 that constrains the implant andprotects it from inadvertent release and resist rotation of the implantthrough interlocking features with the prongs 50 and lock plate 90.Alternatively, sleeve 100 can be omitted and a separate componentprotective end cap can be placed over the implant and instrument toconstrain and protect the implant. When the lock knob 120 is advancedand turned within the instrument 110, the implant is released and thebulges 40 extend as shown in FIG. 2 b.

Implantation into a drill hole 230 in bone 200 is illustrated in FIG. 3a, where the implant is positioned for placement, and in FIG. 3b , wherethe implant is advanced until it is fully within bone and the lock plate90 is in contact with the end face of the bone. Once the implant is inposition, the lock knob 120 is turned in direction 130 to release thelock knob 120 so that it can be advanced in direction 140 with theimplant as shown in FIG. 4a and FIG. 4b . Once advanced the lock knob120 is turned in direction 150, and the implant is released as shown inFIG. 4c . An alternate embodiment exist that does not require theimplant to be advanced out of the instrument 110 and only requires thelock knob 120 to be turned to release the implant. This embodiment usesthe protective end cap.

The instrument is then withdrawn from the implant so that a first end ofthe implant is within bone 200 and the second end extends beyond bone asshown in FIG. 5a . The second bone 210 is then placed so that its drillhole 220 covers the second end of the implant as shown in FIG. 5b . Oncethe bones are approximated, the lock plate 90 is pulled from the implantat the bone interface allowing bone to bone contact to occur as shown inFIG. 5 c.

The implant prongs 50 have a twist along their central axis so that theyare at an angle 170 with the body of the implant. This twist allows theimplant to be rotated and pulled from bone as shown in FIG. 6a , ifremoval is required. When rotated counter clockwise (direction 160), theprongs 50 deflect towards the implant centerline and disengage boneallowing a twisting and pulling motion to remove the implant.

Alternate embodiments of the mandrel 340 can be used with an internallocking prongs 300 with tabs 310 to hold the implant and extend itslength as shown in FIGS. 7a-7c . A second alternate embodiment of themandrel 350 and external locking prongs 320 with tabs 330 can be used asshown in FIGS. 8a -8 c.

The invention and its various embodiments are unique in that the implantfirst locks into a first bone and a second bone and then, when themandrel 190 releases through the lock plate 90, the bulge 40 expands andshortens the implant. With both ends locked into bone, the expansion ofthe bulge 40 pulls together and compresses the bone at the healinginterface. The implant is self-adjusting in that, if it loosens, thebulge 40 further expands, the implant shortens, and the bone is againpulled together and held in contact.

The action of the implant minimizes or eliminates any distance bone mustgrow to fuse the two bone segments. This lack of a gap between the bonesfurther minimizes the possibility of soft tissue migrating between thebone segments and delaying healing. It is further believed that theinterfacial pressure created may stimulate bone healing.

In other embodiments of the present invention, the implant can bedesigned to differently change in length, such as to extend to distracttwo bones. For instance, embodiments of the subject invention includes atubular implant with a plurality of locking prongs, implant lengtheningbone locking extenders, fenestrations in its body, and a lumen for boneingrowth and instrument operation. Such implants can be utilized inapplications in which the two bones are held and maintained indistraction.

This pre-sterilized combination instruments and implant can be packagedwith a drill bit and wires so that the medical procedure kit fullysupports the surgical technique. Hospital costs savings are achievedbecause there is no hospital cleaning or sterilization required and thepatients and hospital benefit from fewer infections and patientcomplications.

Operation of the Invention

The implant embodiments are uniquely suited for fixation of materialsthat have a tendency to benefit from compression or shrink and withdrawso that the fixated structures lose contact. Without limiting the scopeof the invention the illustrated embodiments are used for bone fixation.In bone surgery fragments, separated segments and segments requiringfixation are pulled together by the implant because it is inserted sothat one end is in a first bone segment and the other end is in thesecond bone segment. This method of surgical use is common to bonefixation devices.

The shape changing implant, of the embodiments of the subject invention,exert bone compression force that is not temperature dependent. Thisprovides tremendous advantage for the surgeon and patient over prior artnitinol shape changing implants.

Temperature independence solves problems with the prior art nitinolstaples because the embodiments of the subject invention applyconsistent force prior, during and following implantation. Bodytemperature implants' force changes as the operative wound warms fromnear room temperature to body temperature. This force increase occursafter the wound is closed and without the knowledge of the surgeon cancreate fracture or deformity.

During surgical use the surgeon inserts one end of the implant into afirst bone so that the end, prongs and bulge are fully contained withinthe first bone. The instrument holding the implant elongated is operatedto release the implant. When released the bulge expands pulling theimplant deeper into bone until the implant lock plate resist the pullingforces of the implant. The second implant end is then positioned in asecond bone and this bone is pushed so that the implant is fullycontained within the two bones. Once the bones are in apposition thelock plate is pulled and the two bones are held in contact and undercompression by the shape changing elements of the implant. Oftentreatment of the joints adjacent to where the implant is placed requiretemporary fixation. Surgeons commonly use a sharp tipped stiff wire. Theimplant uniquely allows a surgeon to advance a wire through the lumen ofthe implant into an adjacent joint.

The operation of embodiments can occur with or without the addition ofheat. The preferred embodiment requires no heat other than that of theenvironment, room temperature. Alternate embodiments can be fabricatedso that they change shape at body temperature or with highertemperatures caused by heating strategies such as conduction, inductionor resistive heating.

First, the operation of the preferred embodiment is independent oftemperature in the range of temperatures expected in clinical use andthe use of nitinol. Thus tight control of the material's crystallinestructure transition temperature is not required. Furthermore, thetemperatures are set so that the material is always in its strong andhigh temperature austenitic form. Thus as long as the austenitic finishtemperature is above 20° C. then it will be stable in the operatingtheater and patient's body. So fine chemistry control and post heattreatment to shift transition temperature is not required.

A surgical method for using the implant is illustrated in FIGS. 9-16. Inthe illustrated procedures, the implant within its instrument, the bonecutting instrument, and the wire have been removed from the sterilepackage. FIGS. 9-16 illustrate steps in the procedure.

As shown in FIG. 9, an alignment K-wire is used to create a pilot holealong the centerline of the bone.

As shown in FIG. 10, a cutting instrument with depth stop is used tocreate a drill hole along the bone centerline of the distal bone.

As shown in FIG. 11, a cutting instrument with depth stop is used tocreate a drill hole along the bone centerline of the proximal bone.

As shown in FIG. 12, the intermedullary fixation scaffold is inserted inthe proximal bone drill hole.

As shown in FIG. 13, the intermedullary fixation scaffold is unlockedand knob rotated to release the intermedullary fixation scaffold .

As shown in FIG. 14, the distal end of the intermedullary fixationscaffold is positioned for insertion into the distal bone drill hole.

As shown in FIG. 15, the distal and proximal bones are pushed togetherso that both bones contact the lock plate proceeding the lock plateremoval.

As shown in FIG. 16, k-wire is inserted through an adjacent joint forits treatment, through the intermedullary fixation scaffold and iffurther advanced through a second adjacent joint.

CONCLUSIONS AND SCOPE

The embodiments illustrated in this application are a significantadvancement over the prior art fixation implants such as wires, screws,expanding nitinol implants and multi-component implants in: (1) themethod of operation of the implant and its high strength, (2) the methodof insertion of the implant, (3) its compressive and expansion forcetemperature independence, (4) its efficient implant retention anddelivery system, (5) its compatibility with reusable or single useproduct configuration where all required instruments are sterilepackaged with the implant, (6) its efficient and cost effectivemanufacturing methods, and (7) its minimization of the steps required toplace the device. These advantages are important to musculoskeletalsurgery as well as industrial applications.

Although the description above contains many specificities, these shouldnot be construed as limiting the scope of the embodiments but as merelyproviding illustrations of some of the presently preferred embodiments.Thus the scope of the embodiment should be determined by the appendedclaims and their legal equivalents, rather than by the examples given.

1-21. (canceled)
 22. A method of fixating a first bone and a second bonecomprising the steps of: (a) selecting an implant having (i) a firstbone locking feature at a first end, (ii) a second bone locking featureat a second end, and (iii) a middle section between the first end andthe second end, wherein (A) the middle section comprises an elasticmaterial, (B) the middle section is restrained in an first position byan instrument coupled to the implant, and (C) the middle section in thefirst position has a first length and a first diameter, and; (b) lockingthe first bone locking feature to the first bone; (c) locking the secondbone locking feature to the second bone; and (d) removing the restraintof the middle section to shorten the implant between the first bonelocking feature and the second bone locking feature, wherein (i) theshortening of the implant comprises a shortening of the middle sectionto a second position having a second length and a second diameter, (ii)the second length is shorter than the first length, and (iii) the seconddiameter is different than the first diameter.
 23. The method of claim22, wherein the implant allows bone ingrowth.
 24. The method of claim22, wherein the implant has an expandable surface and the method furthercomprises expanding the expandable surface to lock into the first boneor the second bone.
 25. The method of claim 22, wherein the step ofshortening the implant comprises expanding a surface of the middlesection of the implant to shorten length of the implant.
 26. The methodof claim 22, wherein the step of shortening the implant comprisescontracting an outer surface of the middle section of the implant toshorten its length.
 27. The method of claim 22, wherein the shorteningof the implant imparts mechanical energy to provide interfacial pressurebetween the first bone and the second bone.
 28. The method of claim 27,wherein the step of providing interfacial pressure stimulates healing ofthe first bone and the second bone. 29-30. (canceled)
 31. The method ofclaim 22, wherein the instrument is an internal mandrel or an externalsleeve, wherein the middle section is held under restraint in the firstposition with the internal mandrel or the external sleeve.
 32. Themethod of claim 31, wherein the instrument is an internal mandrel. 33.The method of claim 32, wherein the implant further comprises a lockplate and a lumen, wherein the lock plate is integral to the lumen. 34.The method of claim 33, where the step of removing the restraint of themiddle section comprises using the internal mandrel to rotating the lockplate from a locked position to an unlocked position.
 35. The method ofclaim 22, wherein the middle section forms an expanded bulge when in thesecond position.
 36. The method of claim 32, wherein the expanded bulgeis orientated with the long axis of the middle section of the implant.